X is a random variable following a normal distribution. Given the standard deviation is 12, and Pr(X < 25) = .15, find the mean. Hmm, any help?
Follow Math Help Forum on Facebook and Google+
Originally Posted by scorpion007 X is a random variable following a normal distribution. Given the standard deviation is 12, and Pr(X < 25) = .15, find the mean. Hmm, any help? Consider Z=(X-mean(X))/12, then Z~N(0,1) So if: Pr(Z<A)=0.15 we may look up the value of A which gives this probability. Doing this we find A=-1.03643, so the X=25 corresponds to A=-1.03643 or: -1.03643 = (25-mean(X))/12 so: mean(X)= 25 + 12*1.03643~=37.44 RonL
thanks very much
View Tag Cloud